1. Field of the Invention
The present invention relates to hose fitting assemblies and more particularly to a sacrificial hose fitting assembly, wherein the assembly can be configured to meet predetermined strength pressure and stress requirements in combination with a flexible high pressure hose.
2. Description of Related Art
Many flexible conduits, hoses, cords, wires, and the like are adapted to be connected to stationary objects. A common problem encountered by each of these connections is that the flexing of the conduits, hoses, etc. follows a repeating pattern which tends to concentrate material fatigue in such a manner that the conduit, hose, cord, wire, etc., may break and an early failure may occur. For example, electrical cords for such things as irons, toasters and the like have coiled springs or molded rubber sleeves around them at and in the vicinity of a plug. However, these kinds of devices are quite unsophisticated and do little more than to cause the cord to bend around a larger radius, perhaps with some random differences in the individual bending episodes. Conduits, hoses and the like present other problems since it is not only necessary to protect against fatigue, but it is also necessary to protect against kinking, crimping, sudden pulse-like increase or decrease of internal pressure, and the like. For extremely hostile flexing environments such as road hazards, aircraft, brake lines, etc., the unsophisticated stress relief devices may add relatively little service life.
In some specialized devices, there are even more severe tests to be met. For example, a fuel line hose for an aircraft has a need for a similar kind of stress relief. However, in an aircraft the weight requirements are such that for every pound of added weight, the weight of the supporting structure, power plant, etc. must be multiplied many times. Thus, if a pound of stress relief must be added to the fuel line hose, perhaps as much as 5 to 10 pounds must be added to the weight of the wing spars, landing gear, engine, and the like. In addition, the increased weight adds cost for fuel and a reduction in the operating range of the aircraft on every flight.
A stress relief device should be adaptable to an incorporation into an assembly of the hose and end fitting without a substantial amount of specialized construction. The stress relief should extend over as much of, but no more than, the length of a hose as may be required. A less than adequate amount of protection would be insufficient. More than an adequate amount would lead to excess weight and cost, as well as possible failure.
Some previous stress relievers are designed to protect against a static bending situation, such as with a gasoline pump hose, which may be stretched to its limit and then held in a static position. Under such conditions, a device need not be sophisticated or even optimized because the physical abuse which it must endure is not very great. However, there is a need for hose couplings that can endure a high-cycle, high frequency or continuous, rotary or reversing linear dynamic flexing of the hose, thus withstanding tremendous amounts of fatigue and hysteresis loss.
In addition to stress relief, it is desirable to provide a number of secondary advantages. Exemplary of such advantages are strain relief and abrasion resistance. (Stress relief relates to bending; strain relief relates to pulling.) These advantages are especially important in places where the hose might experience excessive mechanical wear.
Current DOT compliant brake line assemblies for braided metal high-pressure hoses include a strain relief device incorporated into a crimp joint fitting either through a bell deformation of such fitting or a plastic or metal extension to achieve a strain relief effect protecting the high tensile stainless steel wires of the braiding from reaching fatigue levels thereby preventing the rupturing of the inner tubing during the duration of mandated testing.
Therefore, the need exists for a hose fitting assembly and high pressure flexible metal braided hose that can meet DOT regulations, while providing for end user assembly without requiring specialized swaging equipment or additional components extending along the hose.